Klinefelter's syndrome, $(47A+ XXY)$ or $XXY$ syndrome is a condition in which human males have an extra X chromosome. Hence it can be called as a sex chromosomal disorder. Down syndrome or Down's syndrome, (also known as trisomy $21$), is a chromosomal condition caused by the presence of all or part of an extra $21st$ chromosome ($44A+XX$ or $44A+XY$). Down’s syndrome is caused by a meiotic non‐ disjunction event. With non‐disjunction (non‐separation), a gamete (i.e., a sperm or egg cell) is produced with an extra copy of chromosome $21$; the gamete thus has $24$ chromosomes. When combined with a normal gamete from the other parent, the embryo now has $47$ chromosomes, with three copies of chromosome $21$. Turner syndrome $(45A+ XO)$, is seen in human females, of which monosomy $X$ (absence of an entire sex chromosome, ie., $X$ chromosome) is most common. Cri du chat syndrome is a rare genetic disorder due to a missing part of chromosome $5$. Cri du chat syndrome refers to the characteristic cat‐like cry of affected children.